Vitamin C
Preliminary· human dataAlso known as: Ascorbic acid
Important nutrient, but high-dose supplements do little for healthy, well-fed people.
What it is
Vitamin C is an essential nutrient and antioxidant. Deficiency is rare on a varied diet, and for most well-nourished people high-dose supplements do little.
What the evidence shows
Preventing colds. Marketing claim· human data For most people, regular supplements don't prevent colds, though they may slightly shorten one. The famous claims greatly overstate a modest, inconsistent effect.
High-dose antioxidants and training. Preliminary· human data Routinely megadosing vitamin C (and E) around training may blunt some of the adaptations you are training for, because a degree of exercise-induced oxidative stress is part of the signal to adapt.
Who it suits
People with a genuinely poor intake of fruit and vegetables. For everyone else, food easily covers it.
Practical notes
Very large doses commonly cause stomach upset and can raise the risk of kidney stones in susceptible people. Food-level amounts carry neither the adaptation-blunting concern nor the side effects — aim to eat it, not megadose it.
Sources
Frequently asked questions
- Does vitamin C prevent colds?
- For most people, regular supplements don't prevent colds, though they may slightly shorten one. The famous claims greatly overstate a modest, inconsistent effect.
- Should athletes megadose antioxidants?
- Probably not routinely. High-dose vitamin C and E around training may blunt some of the adaptations you're training for, because a degree of exercise-induced oxidative stress is part of the signal to adapt.
- Can't I just eat it?
- Easily — fruit and vegetables provide ample vitamin C for nearly everyone, along with other nutrients. Deficiency is rare in a varied diet.
Related supplements
Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.
Last reviewed: